Before the advent of litters, pet owners had relegated pets to outside the home for lack of an area for taking care of pet excrement. Litters allow pets to take care of waste functions and live inside the home. Housebroken animals, such as cats, are trained into the habit of urinating and defecating in a specially provided litter box. Similarly, untrained and caged animals, such as guinea pigs, urinate and defecate on the floor of their cage, often in approximately the same floor area of the cage. Consequently, pet owners, homeowners, veterinarians and laboratory personnel have added liquid absorbing materials to the litter box or cage to collect the urine and feces.
The most commonly used litter box liquid absorbing materials are inexpensive clays, such as calcined clays, that are safe and non-irritating to the animals, and that absorb substantial amounts of liquids. Other porous, solid litter box absorbent materials, that are used alone or in combination, include straw, sawdust, wood chips, wood shavings, porous polymeric beads, shredded paper, sand, bark, cloth, ground corn husks, and cellulose. Each of these absorbent materials has the advantage of low cost. The entire contents of the litter box including the soiled and unsoiled liquid absorbing materials will eventually be removed, because of the offensive odor caused by the absorbed urine and feces.
Many litters adequately control the odor associated with urine. This is typically done through simple absorption of liquid, which counteracts the growth of odor-causing bacteria. Currently clay soils or comminuted rocks, e.g. the sodium bentonites, are used to improve litter compositions. Sodium bentonites not only absorb liquid waste such as urine, but they also absorb the odor associated with the liquid waste, as the material binds amine compounds in the ‘face sites” of the clay interlayers.
However, clay litters composed of sodium bentonites or other materials do not address the issue of fecal odor. Fecal odor differs from urine odor in that the odor is produced immediately at the time of the defecation, whereas urine odor, being produced by the action of microbes, evolves in the days following urination. Materials in fecal odor that carry an especially strong impact include butyric acid, p-cresol, skatole, and dimethyltrisulfide.